Conventionally, an ion beam irradiation device of this kind, as disclosed in Patent Literature 1, is considered to have a construction that includes an ion source for generating an ion beam, a deflection magnet for deflecting the ion beam from the ion source and an electron source provided on an inner face of a magnetic pole constituting the deflection magnet so that electron beams are irradiated from the electron source to an opposed magnetic pole to thereby suppress the ion beam divergence by a space charge effect (this suppression being also referred to as “neutralization”).
However, since the electrons emitted inside the magnetic pole travel along the magnetic field, the electrons impinge on a magnetic pole opposed to the magnetic pole provided with the electron source and disappear sooner or later. For this reason, there is a problem of low efficiency of using electrons for suppressing the ion beam divergence. In addition, in FIG. 6 etc. of Patent Literature 1, although it is described that the electrons across the ion beam are reflected by providing an insulator or a conductor between the electron source and the magnetic pole, it is unclear how to reflect the electrons and how to make it possible to suppress the ion beam divergence by the space charge effect.
Moreover, since the electron source is embedded in an inner face of the magnetic pole, it is necessary to execute a special process such as providing a concave portion in the inner face of the magnetic pole (see FIG. 5 etc. of Patent Literature 1), and therefore there arises the problems that not only is the structure of the magnetic pole surface complicated but also processing costs thereof are increased. In addition, there is a problem that the processing costs are also increased by the process of providing the insulator or conductor as mentioned above.
In addition, since it is difficult to ensure that a uniform magnetic field is formed by the magnetic pole by complicating the form in such ways as providing the concave portion in the inner face of the magnetic pole or providing the insulator or the conductor, there is a problem that it is difficult to accurately change the direction of the deflection ion beam to be deflected in a desired direction.